algebra set computation using tree structure

tree.rb

class Tree
  attr_accessor :root

  def initialize(root)
    @root = root
  end

  def insert(parent, left, right)
    parent.left = left
    parent.right = right
    left.parent = parent
    right.parent = parent
  end

  def resolve
    root.resolve
  end
end

class Node
  attr_accessor :parent, :left, :right, :operator, :condition

  def initialize(operator, condition)
    @parent = @left = @right = nil
    @operator = operator
    @condition = condition
  end

  def leaf?
    operator.nil? && !condition.nil?
  end

  def resolve
    if leaf?
      condition
    else
      operate(left, right, operator)
    end
  end

  def operate(left, right, operator)
    case operator
    when "AND"
      left.resolve & right.resolve
    when "OR"
      left.resolve | right.resolve
    when "AND NOT"
      left.resolve ^ right.resolve
    else
      raise "unknown operator"
    end
  end
end


root = Node.new("AND", nil)
tree = Tree.new(root)

node1 = Node.new("OR", nil)
node1_1 = Node.new(nil, true)
node1_2 = Node.new(nil, false)

tree.insert(node1, node1_1, node1_2)

node2 = Node.new(nil, true)

tree.insert(root, node1, node2)

puts tree.resolve